Organic electroluminescence devices (which may hereinafter be called “devices” or “organic EL devices”) are capable of obtaining light emission of high luminance with low voltage driving, and thus have been actively researched and developed. Organic electroluminescence devices have an organic layer interposed between a pair of electrodes and utilize, for light emission, energy of the exciton generated as a result of recombination of electrons injected from a cathode and holes injected from an anode in the organic layer.
Improvement in the efficiency of devices has been recently made by using a phosphorescent light emitting material. Further, doping-type devices, which utilize light emitting layers in which a light emitting material is doped in a host material, have been widely employed.
For example, Patent Documents 1 to 3 have proposed organic electroluminescence devices which have improved light emission efficiency and durability, by using iridium complexes, platinum complexes or the like as a phosphorescent light emitting material, and using a compound with a specific structure containing a nitrogen-containing heterocyclic group and a carbazole structure as a host material.
Likewise, organic electroluminescence devices have been proposed, in which light emission efficiency is improved by using a compound with a specific structure containing a nitrogen-containing heterocyclic group and a carbazole structure as an electron transporting material in an electron transporting layer (see Patent Document 4).
The development of host materials also has been actively conducted, and Patent Document 5 describes an organic electroluminescence device, which uses a phosphorescence emitting material and a hydrocarbon-based material in an electron transporting layer adjacent to a light emitting layer. Furthermore, Patent Document 6 describes a phenyl-substituted mCP derivative and an organic electroluminescence device using this derivative.
However, there is need for an organic electroluminescence device having light emission efficiency and durability at a much higher level than the devices described in these Patent Documents.